Analog Inputs test

There is special feature implemented in the software to check noise protection of analog input channels. When this mode is activated, Alarm System CPU is sending all 32 digitized and averaged analog signals once per alarm handling cycle. The number of such samples is given by PC software and may not exceed 255 (restricted to 10-100 by PC software). This allows one to investigate dependence of the statistical error on averaging constant.
The results of the averaged sample measurements are shown on figure and table below. It is obvious that dispersion decreases with increasing number of samples which signal is averaged by. There is no necessity to increase it over 32 for signals with low noise, because the dispersion is almost constant there. Besides, measured value goes higher with increasing averaging number, which is regular and reflects a calculation error during averaging. That is not important for the Alarm System itself, because the shift of the values is negligible (1.5 mV) and comparable to measurement error 1 mV.

Average by 1 2 4 8 16 32 64 128
Dispersion, ADC units 23 18 13 9 6 3 4 2
Dispersion, mV 1.75 1.37 0.99 0.69 0.46 0.23 0.31 0.15

Analog samples with different averaging